/* ----- file I2C_BUS.C66 ----- */
/* Use it for interfacing the devices connected to the I2C-bus */
#include "I2C_BUS.H"
/****************************************************************************/
/* drive bus in inactive state, reenable eventually locked SDA-line */
void I2CInit(void) {
/* re-enable SDA-line */
I2CDelay();
I2CPutSCL(0); /* preset SCL=0 to avoid accidential */
/* transmission of START condition */
/* by following SDA-transition */
I2CDelay();
I2CPutSDA(0); /* drive SDA to inactive state */
I2CDelay();
I2CPutSCL(1); /* set SCL for the first time */
I2CDelay();
I2CPutSCL(0); /* release SCL */
I2CDelay();
I2CPutSCL(1); /* set SCL for the second time */
I2CDelay();
I2CPutSCL(0); /* release SCL */
I2CDelay();
I2CPutSCL(1); /* set SCL for the third time */
/* I2C-bus is now going in the inactive state by the following commands */
I2CDelay();
I2CPutSDA(1); /* this is also the state after RESET*/
I2CDelay();
I2CPutSDA(1); /* setup SCL for START condition */
}
/****************************************************************************/
/* writes a sequence of bytes to a device on I2C-bus */
/* */
/* *SourcePtr: Sourcepointer from RAM */
/* DestAddr: destination-address in I2C-device */
/* Size: length of sequence */
BYTE I2CWrite( BYTE *SourcePtr, BYTE DeviceID, BYTE DestAddr, WORD Size) {
BYTE Result;
I2CStart(); /* send START condition */
I2CWriteByte(DeviceID & 0xFE); /* send ID with cleared RD/WR bit */
if((Result = I2CReceiveAck()) != I2C_SUCCESSFUL) {
/* is device responding ? */
I2CStop();
return(Result);
}
I2CWriteByte(DestAddr); /* write destination address */
if((Result = I2CReceiveAck()) != I2C_SUCCESSFUL) {
I2CStop();
return(Result);
}
while(Size--) { /* loop until all bytes send */
I2CWriteByte(*(SourcePtr++));
if((Result = I2CReceiveAck()) != I2C_SUCCESSFUL) {
I2CStop();
return(Result);
}
}
I2CStop(); /* send STOP condition */
return(I2C_SUCCESSFUL); /* no error occured */
}
/****************************************************************************/
/* reads a sequence of bytes from a device on I2C-bus */
/* */
/* *dest: destination-pointer from RAM */
/* source: source-address in I2C-device */
/* length: length of sequence */
BYTE I2CRead(BYTE *DestPtr, BYTE DeviceID, BYTE SourceAddr, WORD Size) {
BYTE Result;
I2CStart(); /* send START condition */
I2CWriteByte(DeviceID & 0xFE); /* send ID with cleared RD/WR bit */
if((Result = I2CReceiveAck()) != I2C_SUCCESSFUL) {
/* is device responding ? */
I2CStop();
return(Result);
}
I2CWriteByte(SourceAddr); /* write source address */
if((Result = I2CReceiveAck()) != I2C_SUCCESSFUL) {
I2CStop();
return(Result);
}
I2CStart(); /* send START condition */
I2CWriteByte(DeviceID | 0x01); /* send ID with set RD/WR bit */
if((Result = I2CReceiveAck()) != I2C_SUCCESSFUL) {
I2CStop();
return(Result);
}
while(Size--) { /* loop until all data received */
*(DestPtr++) = I2CReadByte(); /* read data */
if(Size) /* send ACK to slave except last time*/
I2CSendAck();
}
I2CStop(); /* send STOP condition */
return(I2C_SUCCESSFUL); /* no error occured */
}
/****************************************************************************/
/* sends START condition on I2C-bus */
void I2CStart(void) {
I2CDelay();
I2CPutSDA(1); /* this is also the idle bus state */
I2CDelay();
I2CPutSCL(1); /* this is also the idle bus state */
I2CDelay();
I2CPutSDA(0); /* generate START condition */
I2CDelay();
I2CPutSCL(0); /* drive SCL to inactive */
}
/****************************************************************************/
/* sends STOP condition on I2C-bus */
void I2CStop(void) {
I2CDelay();
I2CPutSCL(0); /* setup SCL (redundant) */
I2CDelay();
I2CPutSDA(0); /* setup SDA (redundant) */
I2CDelay();
I2CPutSCL(1); /* setup SCL for STOP condition */
I2CDelay();
I2CPutSDA(1); /* generate STOP condition */
}
/****************************************************************************/
/* sends ACKNOWLEDGE condition, i.e. sends an bit-value=0 */
void I2CSendAck(void) {
I2CSendBit(0);
}
/****************************************************************************/
/* receives ACKNOWLEDGE condition, i.e. receives an bit-value=0 */
BYTE I2CReceiveAck(void) {
if (I2CReceiveBit() == 0)
return(I2C_SUCCESSFUL); /* must be 0 if device responds */
else
return(I2C_NO_ACKNOWLEDGE);
}
/****************************************************************************/
/* sends one bit to I2C-bus, also used for sending ACKNOWLEDGE condition */
void I2CSendBit(BYTE State) {
I2CDelay();
I2CPutSCL(0); /* setup SCL (redundant) */
I2CDelay();
I2CPutSDA(State); /* setup SDA */
I2CDelay();
I2CPutSCL(1); /* enable SDA writing */
I2CDelay(); /* let SCL get stabilized High */
while(!I2CGetSCL()); /* wait until SCL-line is released */
I2CDelay();
I2CPutSCL(0); /* disable SDA writing (SDA is now */
/* clocked) */
I2CDelay();
I2CPutSDA(1); /* release SDA */
}
/****************************************************************************/
/* receives one bit from I2C-bus, also used for receiving an ACKNOWLEDGE */
/* condition */
BYTE I2CReceiveBit(void) {
BYTE State;
I2CDelay();
I2CPutSCL(0); /* setup SCL (redundant) */
I2CDelay();
I2CPutSDA(1); /* setup SDA for input (TRISTATE) */
I2CDelay();
I2CPutSCL(1); /* enable SDA reading */
I2CDelay(); /* let SCL get stabilized High */
while(!I2CGetSCL()); /* wait until SCL-line is released */
I2CDelay();
State = I2CGetSDA(); /* read SDA state */
I2CPutSCL(0); /* disable SDA reading (SDA is now */
/* clocked) */
I2CDelay();
return(State); /* return state */
}
/****************************************************************************/
/* sends a byte to I2C-device */
void I2CWriteByte(BYTE TransferData) {
BYTE Loop;
for(Loop = 0; Loop <= 7; Loop++) {
I2CSendBit((TransferData & 0x80) == 0x80);
TransferData = (TransferData << 1);
}
}
/****************************************************************************/
/* reads a byte from I2C-device */
BYTE I2CReadByte(void) {
BYTE Value, Loop;
Value = 0;
for(Loop = 0; Loop <= 7; Loop++) {
Value = (Value << 1); /* 1. shift doesn't affect (value=0) */
Value = Value | I2CReceiveBit();
}
return(Value); /* return byte read */
}
/****************************************************************************/
/* ----- end I2C_BUS.C66 ----- */